1. Technical Field
This invention relates to audio systems, and more particularly to an audio power management system for use in an audio system.
2. Related Art
Audio systems typically include an audio source providing audio content in the form of an audio signal, an amplifier to amplify the audio signal, and one or more loudspeakers to convert the amplified audio signal to sound waves. Loudspeakers are typically indicated by a loudspeaker manufacturer as having a nominal impedance value, such as 4 ohms or 8 ohms. In reality, the impedance of a loudspeaker varies with frequency. Variations in loudspeaker impedance with respect to frequency may be shown with a loudspeaker impedance curve, which is typically provided by the manufacturer with a manufactured model of a loudspeaker.
A loudspeaker, however, is an electromechanical device that is sensitive to variations in voltage and current, as well as environmental conditions, such as temperature and humidity. In addition, during operation a loudspeaker voice coil may be subject to heating and cooling dependent on the level of amplification of the audio content. Moreover, variations in manufacturing and materials among a particular loudspeaker design may also cause significant deviation in a loudspeaker's pre-specified parameters.
Thus, loudspeaker parameters such as the DC resistance, moving mass, resonance frequency and inductance may vary significantly among the same manufactured model of a loudspeaker, and also may change significantly as operating and environmental conditions change. As such, an impedance curve is created with a large number of relatively uncontrollable variables represented as if all these uncontrollable variables were fixed and non-varying. Accordingly, a manufacturer's impedance curve for a particular model of a loudspeaker may be significantly different from the actual operational impedance of the loudspeaker. In addition, an acceptable range of variations in the audio signal driving the loudspeaker may also vary based on the loudspeaker parameters of a particular loudspeaker and the operational conditions.